Piston



Oct. 12, 1937.

J. 5. DONALDSON PISTON Original Fili ad'April 14, 1933 4 Sheets-Sheet 1 L4 ATTORNEY Oct. 12, 1937; .1. s. DONALDSON 2,095,331

' PISTON v ori inal lfiled April 14', 19s: 4 Sheets-Sheet 2 ill Lllllllll/llllll lly/ l Z? t INVENTOR "W -l ATTORNEY J. 5. DONALDSON Dag-12, 1937'.

Original Filed April 14, 1933 4 Sheets-Sheet 3 lNV TOR L; ATTQRNEY Oct. 12, 1937. J. s. DONALDSON 7 I 2,095,381

- PISTON Original Filed April 14, 1933 4 Sheets-Sheet 4 INVEETOR I L: ATTORNEY Patented Oct. 12, 1937 PISTON 1 John Shear-man Donaldson,

r oF lcs.

St. Albana, N. Y., as

signo'r to Donaldson Piston Corporation, Belleville,

N. 3., a corporation or New Jersey.

Application April 14, 1933, Serial Renewed February 24, 193'! No. seams 6Claims. (chaos-2o) M This invention .relates to pistons, and more particularly pistons for use in internal combustion engines.

It is necessary for proper operation of an '5 internal combustion engine to have a piston which ts the cylinder reasonably well at all times. I! either the cylinder or the piston or both wear, thewell known piston slap develops. If the pis ton is made 01' a light allo base ,alloy, having a diflerent, usually ,higher, coemcient of heat expansion from that of the cylinder, the piston will, as a result, not fit periectly at all times. If it fits when hot and expanded, it will be loose and slap when cold 16 and contracted; if it flts when cold, it will bind and seize when hot.

One of the objects .of the present invention is to provide a piston which will automatically take up wear.

a piston constructed so that relative expansion and contraction of. the piston and cylinder are automatically compensated for:

Another objectof the invention is the pro--" vision of a pistonwhich may be removed and reinserted either wholly or in part through the top of the cylinder for renewing the rings or other purposes.

An additional object of the invention is the provision of a piston having separable skirt and ring portions, the skirt portion being connected to the head of a connecting rod in such a way that the ring portion may be detached from the skirt portion without interferingwith the connectlon between the skirt portion and the connecting rod.

Other objects and advantages of the invention will appear from the following description of two approved embodiments of the invention shown,-

by way of example, in the accompanying draw-' ings. The invention accordingly consists in the various features of construction, combinations 01- elements and arrangements of parts which are exemplified by the constructions hereinafter set forth. The scope of the invention is indicated by the appended claims.

In the accompanying drawings:

Fig. 1 is a vertical sectionalview of one-form .of piston on the line l--l of Fig. 2, with parts in elevation:

Fig. 2 is a plan view of the piston with the capremoved and parts broken away;

Fig. 3 is a view taken on the line 3-3 of Fig. 1 showing two skirt sections in bottom plan view and the other skirt section in cross section;

A further object of the invention provide Fig. 4 is a top plan view of the piston cap;

Fig. 5 is a sectional viewon the line 6-4 of.

Fig.

Fig. 6 is a plan view of thelock washer which such as an aluminium holds the cap screw in place holds the upper part oi the connecting rod head bearing in adjusted position; 7 Fig. 7 is a sectional 'view on the line l--| of Fig. 6; p

Fig. 8 is a bottom plan view of the upper part of the connecting rod head bearing;

Fig. 9 is a vertical sectional view of a modified form of piston on the line 9-8 of Fig. 10, with 1 parts in elevation;

Fig. 9, showing two sldrt sections in bottom plan view and the other skirt sectlon'ln cross section;

Fig. 12 is a top plan view oi the cap of the modified form of piston; Y

Fi 13 isa sectional view on the line l3- 3 of Fig. 12;

Fig. 14 is a top plan view of the'piston skirt sections of the modified form of piston, with a part broken away; I

Fig. 15 is a plan view of .one of the piston rings for both forms of construction;

Fig. 16. is a plan view of the lock washer which in the modified form of construction; I

Fig.1? is a perspective view of one of the piston ring pusher blocks for both forms of construction;

nected to a connecting rod 24 by a ball and socket joint, the ball 25 of which is detachably mounted on the end of the connecting rod. The end of the connecting rod is formed with a right-hand thread adapted to engage a corre-. sponding thread in-a recessed portion ofthe ball. A left-hand screw 26 extends slidably through an 'aperture in the rtop of the ball and engages a threaded central recess in the end oi the rod.

In assembling these parts, the ball is screwed down on the top 01' the connecting rod. en the screw as is screwed in until its head. engages the "wan of the chamber 21 (Fig. 2).

washer with its projections in engagement shoulder of the aperture in the ball. The latter cannot then unscrew from the end of the connecting rodsince any unscrewing movement of the ball tends to urge the screw 26 further into its recess. I

The body 20 is formed with a central cylindrical chamber 21 therethrough for of upper and lower bearing blocks 30 and 3!, respectively. The upper block has threaded engagement with the wall of this chamber, so that by rotating this block its axial position within such chamber may be adjusted. The lower bearing block rests on a shoulder 32 at the lower end of this chamber. The lower bearing block is annular in form, the inner diameter of the annulus being large enough, not only to permit the passage of the end of the connecting rod therethrough, but also to permit the latter to move laterally to the desired extent. This block has a spherically curved annular inner surface adapted to contact with the under surface of the ball. The upper bearing block is provided with a spherical under surface adapted to contact with the top of the ball. The top 33 of this block has a hexagonal or similar shape so that the block may be turned by a socket wrench or the like. v

The upper surface of the upper bearing block around the hexagonal top 33 is formed with a series of radial corrugations or grooves 34 (see Fig. 2). After the upper bearing block has been brought into adjusted position, it is locked in such position by an annular washer 35 providedwith two. projections 36 on its under surface. Each of these projections extends into one or other of the corrugations or grooves 34, so that, so long as these projections are held in engagement with any given pair of corrugations, the bearing block cannot turn relatively to the washer. Turning of the latter with respect to the body 20 is prevented by forming the washer with a peripherally projecting lug 31 which engages a vertical slot in the To hold the with the corrugations on the upper bearing block, an annular castellated lock nut 38 is provided having threaded engagement with the Walls of the chamber 21; Accidental unscrewing of this nut is prevented by a cotter pin 40 inserted through a hole in the body 20 and one of the slots in the castellated portion of the nut. The interior portion of the lower part of this nut is given hexagonal form for engagement with a suitable form of wrench.

, There .are about adjusted to /34 of a revolution. This delicate adjustment allows relatively coarse and hence strong threads to be used on the bearing block 33. The castellated nut has only 16 slots, so that its position can be adjusted only to of a revolution, or only one-fifth as accurately as the bearing block and washer. Hence, the interposition of the washer 35 between the upper bearing block 30 and the lock nut 38 increases the delicacy of adjustment of the bearing block aboui five times for pitch.

The cup-shaped head 22 of the piston is pro vided with an upstanding portion 4|, apertured for the passage of bolts 42 by which such part 22 isdetachably secured to the body.

The head 22 is also formed with three threaded the reception 84 of the grooves 34, so that/ the position of the upper bearing block 30 may be 'tically slotted at six threads on the block30 'of equa each of these slots apusher block 5| is slidably is formed with to the head 22. The cap 23 out interfering with either the setting of the connecting rod end bearing blocks or the connection of the head to the body 20. After the cap has been removed, the head 22 can be removed without disturbing the setting of the connecting rod bearing blocks.

A part of the body 20 is formed with an annular recess to receive the lower body portion of the head 22 so that these body portions of the piston are thereby held in concentric relation to each otherindependently of the bolts 42. Similarly, the cap 23 is formed on its under side with an annular recess to receive the upstanding edge of the cup-shaped head 22 and is thereby held in concentric relation-therewith.

The top surface of the cap is formed with three recesses 39, the bottoms of which slope downwardly in directions transverse with respect to the radii of the piston. Looking down on the top of the cap, the direction of downward slope is clockwise. Intermediate each of these sloping surfaces are surfaces lying in radial axial planes. It has been found that a piston constructed,.and associated with a connecting rod, as previously herein described, rotates intermittently through angles of a varying number of degrees. It has been observed that this rotation in the, normal operation of the engine is in a clockwise direction, viewing the piston from above. The cause of the intermittent rotation of the piston through varying angles is believed to be due to forces developed of the recesses 39 rests in appropriate position causes a movement of the piston about its axis and that this movement is irregular owing to variations in the explosive forcesand varying angularpositions of the radial rising surfaces of the piston head when the forces are applied. Whatever the correct theory may be in regard to this, the fact is that the piston rotates in variable increments, distributing wear and eliminating the possibility of wearing grooves or scores as would result from rotating the piston in definitely fixed angles or from holding it against rotation.

The turning of the piston tends to equalizethe wear on the piston and/or cylinder, unless the cylinder is unequally worn at the time the present form of piston and connecting red are installed, in which case the wear on the parts of the cylinder having the smallest diameter tends to be the greatest, and vice versa.

The piston rings 5|! are carried by the head 22 and may, therefore, be replaced without removing the entire piston, and therefore, without disconnecting the body 20 and the skirt 2|, carried thereby from the connecting 'rod. All that is necessary is to take off the cylinder head by removing bolts 44, cap 23 and bolts 42. The ring portion or head 22 may then be lifted out of the cylinder.

The piston head 22. The peripheral wall of the head is verequidistant points, and in mounted. As shown in Fig. 17, the outer face of each pusher block has three recesses 52 to receive the pistonrings. The inner face of each block a recess 53 for the reception of the rounded end of one of three leaf springs 54. a

The latter press the pusher blocks outwardly and thereby exert a symmetrically distributed pressure on the piston rings. The mid-points of inner faces of the rings to receive extending webs or flanges 6|. center of each section is a spect to the flanges 63 projection on the center of each spring without perforating the latter. A hole or recess is. drilled in each of the spring seats in receive such projection.

Each piston ring is desirably formed of a single piece and it is advantageous to arrange the point at which the ends of each ring overlap at about 120 from the corresponding point for the other two rings. This is accomplished by forming shallow vertical grooves or recesses 60 on the the pusher blocks 5i and so prevent rotation of the rings with respect to the piston and keep the rings in the desired relative position. c

the portion ll to The skirt of the piston is formed of three sections 2|, each comprising a thin curved outer wall, stiffened top and bottom by horizontal inwardly Adjacent the pair of flanges 62, adapted to fit slidingly between a corresponding pair of flanges 63 on the central body 20. Lateral movement of each pair of the flanges 62 with reis prevented by a rectangular block 64 held in position between the flanges 63 by a threaded pin 65. The flanges 62 are slotted vertically to receive sections are, therefore, free to slide radially in and out, but are restrained from moving laterally or longitudinally-with respect to their supporting body 20. These skirt sections are yieldingly pressed outwardly ag der by leaf springs 16 shallow depressions in at their ends against the skirt sections between the flanges 62, 62. These springs are held in place longitudinally by forming projections thereon forengagement with small recesses in the frame 20 (Fig. 3).

The piston skirt is conveniently formed from a single casting which is machined to flt the cylinder and body 20 and thenslit longitudinally to form the three sections. If rotate and the sections were seated at their centers in out exactly parallel to the axis of the cylinder, ridges would be formed on the walls of the cylinder opposite the spaces between the sections. While rotation of the piston substantially prevents the formation of such ridges, wear may be therein, through which drops of oil may pass. It

will be noted that the body 26 is cut away between each pair of vertically and radially arranged webs or fins 12 which support the flanges 63, and through these cut away parts oil is thrown inwardly and through the; apertures 1 I. This construction permits oil to be thrown upwardly from the crank-case into the head, from which it finds its way down through a central aperture 13 in the upper bearing block 30 to grooves I4 which distribute the oil at the bearing. 70.

' in and out of the chamber formed by the head The same open construction of the body and the apertures H in the head which permits passage of oil, also allows air to circulate and flow 22 and the cap 23. This circulation and flow of air alds'v ry materially in keeping the springs 64 this block. The skirt nst the walls of the cylinthe-blocks 64 and bearing the piston did not cool and is sufflcientto prevent the latter reaching such a temperature thatthey lose their elasticity.

It will also be noted that the head 22 and the body 20 are in contact over a relatively very small area as compared with the efiective cross-sec-- tional area of the piston. This construction restricts flow of heat fromthe upper part of the piston to the lower central body. Further, the webs 12 of the latter serve as cooling flns so that little heat is transmitted the skirt sections 2|.

The body. skirt, head and cap may all be made of a light alloy, although such alloy may have a considerably higher coeflicient of heat expansion than the metal of the cylinder. The cap and the head havea diameter small enough so that there is still clearance at the maximum piston temperatures, as these parts do not haveto fit the cylinder walls closely. The piston is guided in its travel up and down in the cylinder by the skirt, and the passage of gases around the cap' through the body to and head 22 is prevented by the piston rings.

The skirt is constructed so that it can expand or contract radially, the springs 10 maintaining the outer surface of the skirt in constant contact with the cylinder walls at all times and under all conditions.

A- suitable alloy has the following typical composition: copper 4%, magnesium 1.5%, nickel 2%, and aluminum the balance. Other alloys having diflerent proportions and/or ingredients may also be employed.

d A modified form of construction is shown in Figs. 9 to 19, inclusive. As in the first form of construction, the piston comprises four main parts, a central body 20a. a skirt 2la' surrounding such body formed of three separate sections, a cup-shapedhead or ring portion 22a and a. cap 23a. The body is connected to a connecting rod .241: by a ball and socket joint, the ball 25a of .which is mounted on the end of the connecting rod. This ball 25a is not detachable, as in the first form shown, but is made an integral part of the connecting rod. The socket consists of an upper bearing block 30a having a cylindrical outer surface so that it may slide vertically in a chamber 21a in the body, arra iged concentrically with respect to the piston as a whole, and a lower bearing block formed of a plurality of separate sections 3la. The lower part of the wall of the: chamber 210. converges downwardly and the outer surfaces of the bearing sections 3la are formed complementarily so that such sections are firmly supported thereby. Both the upper and lower bearing blocks are formed with spherically curved inner surfaces for ,en-

gagement with rod. 1

The minimum diameter ofthe chamber 21a is greater than the maximum diameter of the ball 25a, so that, by lowering or raising thepiston, the ballmay be introduced into or removed from such chamber. The lower bearing block is the head 25a of the connecting made in a plurality of sections fitted-together The'sections are put dropping the piston piston into its most accessible position, but also to bring the connecting rod into vertical position and thereby bring the upper surface of the projection 15 into horizontal position. The next step is to remove the cap 23a and head 22a. Then the body a is pushed down to force the ball 25a through the chamber and with it push the upper bearing block out of such chamber. Further downward movement of the body causes the projection 15 to engage the lower surfaces of the sections 3|a. As the top of the projection 15 is horizontal, it engages all of the sections simultaneously and then lifts them, without disturbing their position around the connecting rod. The sections can then be removed by the fingers. The parts are re-assembled by placing the sections 3|a on the projection 15, and finally raising the body to seat the sections on the lower part of the chamber and then seat the ball 25a on such sections, as shown in Fig. 9.

The head or ring portion 22a of the piston is provided with three upstanding bosses 16, centrally apertured for the passage of bolts 420. by which the head is detachably secured to the 0 :1.

The head is also formed with a central boss 11 with a threaded axially located aperture for the reception of a threaded member 18. The member 18 is vertically above the upper bearing block a, so that, by turning such member, the upper bearing block may be set in adjusted position with respect to the ball 25a. The top of the member 18 is slotted for engagement with a screw-driver. A lock nut is provided for clamping the member 18 in adjusted position.

The cap 230. is formed on its under side with an annular recess to receive theupstanding edge of the head 22a and is thereby held in concentric relation therewith. It is releasably clamped down on the top of the head by a bolt 8| engaging a threaded aperture in the member 18.

The aperture 82 through which the bolt 8| passes is made of considerably greater diameter than the bolt and is tapped, so that, should the cap stick to the head after the bolt 8| has been removed, a bolt which fits the aperture 82 may be screwed into the latter until its end engages the top of the member 18. Further rotation of such bolt will force the cap 23a away from the head. 7

The bolt 8| is held in place by means of a washer 83 having a lateral projection 84 extending from its outer periphery and a projection 85 extending from its inner periphery. The aperture 82 has a keyway 88' cut therein of a width suflicient to receive the projection 85 when the latter is bent downward. The engagement of the projection 85 with the keyway 88 prevents turning of the washer. After the bolt 8| has been screwed home, the projection 84 is bent upwardly against the adjacent face of the head of the bolt to prevent the bolt turning relatively to the washer and thereby to the cap.

The top surface of the cap is formed with three recesses 3511 the bottoms of which, as in the first form of construction, slope downwardly in directions transverse with respect to the radii of the piston. Looking down on the top of the cap, the direction of downward slope is clockwise. As in the first described construction, the piston is caused to rotate through variable angles under normal operating conditions of the engine. Thus the piston has a rotary, as well as a longitudinal, movement.

To ensure that the piston turns as a unit instead of the cap only turning, the under side of the latter is provided with three downwardly extending lugs 98 (Figs. 10 and 14), which engage with opposite sides, respectively, of radially disposed webs 9| on the head.

The piston rings 50 and their pusher blocks 5| are of the same construction as in the first form of piston and, hence, need not be described again. It will be noted, however, that, while the two lower rings are mounted in grooves in the head, the top ring is arranged in a groove formed by a recess in the headand the adjacent part of the cap 23a.

The pusher blocks are pressed outwardly by leaf springs 540.. These springs are held in place longitudnally by punching a projection on the center of each spring without perforating the latter. A hole or recess is drilled in each of the spring seats in the bosses 16 to receive such projection. v

The skirt of the piston is formed of three sections 2|a, each comprising a thin curved outer wall, stiifened top and bottom by horizontal inwardly extending webs or flanges 6|a. Adjacent the center of each section is a pair of flanges 62a, adapted to fit slidingly between a corresponding pair of flanges 63a on the central body 20. Lateralmovement of each pair of the flanges 82a with respect to the flanges 63a is prevented by the engagement of a projection on the lower of the two flanges 62a with an aperture 96 in the web 91 of the body. The skirt sections are, therefore, free to slide radially in and out, but are restrained from moving laterally or longitudinally with respect to their supporting body 28. These skirt sections are yieldingly pressed outward against the walls of the cylinder by leaf springs Illa, seated at their centers in shallow depressions in the webs 91 and bearing at their ends against the skirt sections between the flanges 62a, 62a. These springs are held in place longitudinally by forming projections thereon for engagement with small recesses in the webs 91 (Fig. 11).

The piston is designed for splash lubrication. For this purpose the bottom of the head 22a has a series of apertures I00 therein, through which drops of oil may pass. It will be noted that the body 20 is cut away between each pair of vertically and radially arranged webs or flns 12a which support the flanges 63a, and through these cut away parts oil is thrown upwardly and into the apertures I08. This construction permits oil to be thrown upwardly from the crankcase into, the head, from which it finds its way through apertures |0| and I02 in the head and upper bearing block, respectively, to the bearing surface of the connecting rod. As in the first form of piston, this open construction ofthe body and the apertures H10 in the part 22a which permits passage of oil also allows air to circulate and flow in and out of the chamber formed by the head 22a and the cap 23a.

What is claimed is:

l. A piston comprising a central body portion, a skirt portion anda piston ring portion above the skirt portion removably attached to the central body portion, and upper and lower bearing means in the central body portion shaped to receive the ball head of a connecting rod,-the upper bearing means being removable in an upward' direction from the ball head and the lower bearing means being sectional to permit removal from or placement in bearing position when the ball head and central body portion are given a certain relative axial movement permitted by removal of the piston ring portion and the upper bearing means.

2. A piston comprising a central body portion having a seat for a bearing, and means for slidably mounting a sectional skirt and means for 10- cating a piston ring portion thereon in vertically spaced relation from the sectional skirt, a skirt comprising sections slidable respectively toward and from the central body portion and spring pressed therefrom, lower bearing means for a connecting rod head seated in said central body portion, upper bearing means for said head adjustably fitted in said central body portion, means for securing the upper bearing means in adjusted position, a piston ring portion, and means for detachably attaching the piston ring portion in position on the central body portion, the said central body portion being shaped to permit removal of the piston ring portion in an upward direction and to permit removal in an upward direction of the upper bearing means and its securing means whereby access to the connecting rod head and lower bearing means is provided,

and the piston ring portion being shaped to permit removal of the upper bearing means when said portion is in located position on the central body portion.

3. A piston having a'central body portion, ad-

justable bearing means for the: ball head of a connecting rod, said means being ,removably mounted in the central body portion, means in the central body portion for securing thesaid bearing means in position, a ring portion removably secured to the upper part of the central body portion, a skirt comprising a plurality of separately movable sections slidably mounted on said central body portion for movement toward and from said central body portion and spaced below said ring ing the skirt sections outwardly.

4. A piston having a central body portion proportion, andv spring means urg-' mounting skirt sections,- adjustable 1 bearing means for the ball head of a connecting rod, said bearing means being removably mounted in the central body portion, a piston ring portion removably attached to the upper part of the cenpressed outwardly from the central body portions and mounted thereon to locate the top of the skirt sections downwardly spaced from the ring portion, and at least three spring pushers in the ring portion adapted to bear at as many points on the inner side of rings in the ring portion.

'6. The combination of a piston and connecting rod; the piston comprising a body carrying a skirt portion and a piston ring portion, means for detachably securing the ring portion to the body, said body having a central chamber \there-. in, a ball head on the connecting rod, upper and lower bearing blocks in said chamber for the engagement of the upper and lower surfaces of said ball head, the upper block having threaded engagement with the walls of said chamber, means for locking said upper block in adjusted position, the upper surface of the upper block being formed with a series of indentations, a ring having 'a projection on the under side adapted to enter one of said indentations, an outwardly projecting lug on said ring adaptedto extend into a vertical recess in the wall of said chamber, and means for holding said ring against the upper surface of the upper block to prevent rotation 01 the latter.

JOHN SHEARMAN DONALDSON.

vided with circumferentially spaced-means for 

